Magnetotelephone arrangement for direct current



z- 8, 1950 c. s. RHOADS 2,518,374

MAGNETO TELEPHONE ARRANGEMENT FOR DIRECT CURRENT Filed Dec. 5, 1946 lNVE'NTOR By c. s. RHOADS ATTORNEY Patented Aug. 8, 1950 UNITED PATENT "OFFICE MAGNETO TELEBHONE ARRANGEMENT-FOR DIRECT CURRENT 4 Charles S. @Rhoajds, Yonkers, N. Y., assignor-to Bell Telephone. Laboratories, Incorporated, New 'TY'OIKN; Y.,"a"'corporaticnfcr New York Application' Dc'ceniber 5, 1946, Serlal1No. 714,209

I 3 Claims;

-'I-hi invention relates to telephone seteircuits and more particularly --to portable telephone set circuits, employingia, .ha-nd generatoror: magneto.

An object of this invention =is to, make use of the "hand generator output of a =magnetotele- .aphoneset. for-other than or in acldition'to signal- -ing purposes.

Ma netotelephone sets, as is wellknown-inthe art, include a hand generator, a receiver circuit,

"a transmitter circuit,-and a local battery. The

local battery usually consists'of two or moredry batteries. The hand generator "whencranked at .usual speed developsalternatingcurrent-at a low ,=frequency rate customarily substantially twentycycle per second frequency. The ihandegenerator ,-current-of this frequency =;customarily is for op eratingpolarizedbells of other suchmagnetQteIe- ;phone sets, and also for operating signal receiv- -ing devices Such-as 'magnetoswitchboard drops, coldcathode tube signals, etc.- that may beconnectedtomagnetotelephone lines.

1 1 Portable'magnetotelephonesets usuallye'include ahand generator, and a handset includinga transmitter, a receiver anda device to closethe circuit from-the local ba-ttery to the transmitter. V fl'hisdevice-can be-operated'by the fingers of the hand that holds thehandset, and is, usually called the push-to-talk switch.

Light weight is desirable inportable-magnetotelephone sets and in some ,practical or zcommercialt designs smallso-called flashlight dry batteries are used to'supply the -transmitter .current 1 to ;minimize weight.

Other designs may, use larger so-called six-inch dry batteries. Whether .thedry batteries; are-largeor. small, they aresubv.ject. to :various adverse-effects. :In .cold climates where temperatures ma fbecome zero or lower dry batteries freeze which reduces their voltage so much thattheir outputbecomes insufficient [for satisfactory telephone transmission. In 'hot humid climates drybatteries-deteriorate rapidly.

'In any. climate 'dry battery life'is comparatively short due'to the energy consumption from use and also from internal chemical action when idle. Asa resultofthesehclimatic, use and age 'fflfects, 'ma'gnetotelephone dry Ibattery w performanc is variable and unreliable.

Thehand generator in'a ma'gnetotelephone set usually is a reliable device and is little afiected byclimateguse or age. One of the objects of r thisinvention'is tofp'e'rmit use of then-and generator as a reliable source of transmitter'current either, as asupplement t the conventional bat- Ytery-sour ce, or as a sole-source of the transmitfter or"talking currentfor the magnetotelephone i'l Thls' invention accomplishes this; object'by .pro-

l'viding means for 'convertingjtheialternatingg'cur- 're'ntoutpiitpf the ,hand'gerie'ratorto direct ourrentis'm'oothmg out this direct current by'aiiilter '2 --ing=dev ice andsusing the resultingdirect current .in' the transmitter circuit of the magnetotelephoneset.

I iOther-objects and-features of the invention will appeargmore fully from thepdetailed-description thereof hereinafter given.

Although apreferred-formof-the inventionrrd dates to aiportable.magnetotelephone-set, it is .not limited thereto. -Also the'use ofthe converted current of the hand generator is I not limited to use as-transmitter current hut, invaddition tcor instead of;ma -be--mad available for other uses, .for example, as power supply toa vacuum tube amplifier toincrease-the volumeof receiver voice 1 current waves inlthe telephone set.

A more complete understanding of theinventlon may be obtained .from thedetailed description that 7 follows when read in connection with the accompanying drawing,the single figure-of which is-illustrative of a magnetotelephonev et ,circuitembodying the invention.

1 '-With reference to the drawing, 7 the circuit. con- --fi-guration and the character of the components -ofthe .circuit of atelepho-ne set in. accordance withthis invention are shown. The telephone set-comprises a pair of line terminals l diu ean'im coming signal. device or polarizedbell 30, amultiwinding inductioncoil or transformer .43, a telephone. receiver -50, a telephone. transmitter ,EU, condenser-s10 andMfl for. inclu'sionin the speech currentcircuitsof .theset, a source of current .or 'local' battery '83, a normally ,openpair of contact springs or contactsS'O, a'key operated switching means-ordevicellflt which locks or .remainsin the operatic-nposition when adjusted, moved or -thrownirom its normal or non operated position.

All "these components' may be "housed or supported-within or on a single container or unit,"the receiver. andrthe transmitter may be'inclu'ded in ahan'd-set, or in a chest transmitter and head- .set, and be connected with the circuitthrough a :suitable cordor. cords. Thetelephone receiver may be of the type disclosedin L. A. "Morrison etaljPatent 2,220-,943, of November 121.9%; for :Acoustic Device, and the telephone transmitter may; be of the type shown in A. FJ'Bennett et a1. 'Patent 2,042,822 of June'2,,1936, fori'ielephone Transmitter. The rectifying means 2a mayf'be of the so-called full wave copper oxidetype. The filtering means I30 may be of the retardationtcoil and condenser'type. The switchingdevice I56 may comprise a manually operable two-position key or. button and four sets of 'contactspring pile ups. This switchingdevice N10 is shown'in its normal or'non-operated position under which condition contact pairs l, and l are open and contactpairs 2, 4, v6 and 8 are closed. When 'thefrkey is operated, contactpairs Ejflytand 8 are openedand pairs|,"3, 5 and! are closed. The 'con'tact'swltch 'SO'may be, ofithe so calle'd pushuser when not talking may economize with respect to the local battery 80 as well as minimize noise pick-up by the transmitter.

The multiwinding transformer 40 comprises three windings AI, 42 and 43, serially connected with the condenser I across the line terminals I0, 20. The transmitter 60, contact pair 90, contact pairs 6 and 8 of the switch I09, and the local battery 80 constitute a series-connected circuit across winding 42 of the induction coil. This battery and transmitter circuit is the normal circuit and is for use when the batteries are in condition to provide satisfactory outgoing transmission from the telephone set. The receiver 50 is connected across the series-connected transformer winding 43 and condenser III. The windings of transformer are wound on a common core and together with the receiver and transmitter constitute an anti-sidetone circuit of the type shown in schematic in Fig. l of K. S. Johnson Patent 1,396,760 of November 15, 1921, for Signaling Circuit. The winding 43 is proportioned so as to include sufiicient resistance to constitute the balancing network or resistance in shunt with the receiver.

. When signaling current is incoming to the telephone set circuit at terminals Iii, 28 thereof, supplied for example over a suitable line, for example, the standard steel Wire telephone pair,

such as is used in military field telephone systems, and from an exchange or switchboard, for example, at the field headquarters point, the polarized bell 3B is actuated over a path from line terminal II], polarized bell 30, to line terminal 20. When the switching device is in its normal or non-operated position, with the receiver at the ear and the transmitter adjacent the mouth, the called party, after closing the pushto-talk switch 90, may respond and transmit speech currents out of the set circuit making use of local battery 89, through line terminals It, 213 and receive speech currents incoming over the telephone line through the terminals ID, 20.

When it is desired to signal outwards from the telephone set to the line, the hand generator III! is cranked by means of the handle provided on it for that purpose. With key or switch H30 in its normal or non-operated position, the hand generator I00 is serially connected from line terminal I0 through normally made contacts 2 and 4 of switch I00, to line terminal 20. As is well known in the art, hand generator I I0 includes an automatic contact closing device III, which closes a pair of contacts in a pile-up of contact springs when the crank of the hand generator is turned and which contacts automatically open to their non-operated condition when cranking ceases. v

The rectifying device I2!) can be of the copper oxide type for full wave rectification which is a type of rectifier well known in the art "but is not limited thereto. The filtering unit I30 can comprise, for example, but is not limited thereto, of two condensers I3I, I33, and an impedance coil The procedure to be followed when it is desired to make use of the hand generator as a source of'transmitter current is as follows: The switching device I00 is adjusted or moved to its locking rectifier device 4 position whereby contact pairs 2, 4, 6 and 8 are opened and contact pairs I, 3, 5 and I are closed. The opening of contact pairs 2 and 4 disconnects the hand generator circuit from the line terminals I0 and 20. The closing of contact pairs I and 3 connects the hand generator circuit to the I20. The opening of contact pairs 6 and 8 disconnects the local battery from the transmitter circuit. The closing of contact pairs 5 and I connects the circuit of the filtering device I30 to the transmitter circuit. With the receiver 5|] to his ear and the transmitter 60 adjacent his mouth the user of the telephone set will crank the hand generator IIU to develop its full voltage and then after closing the push-to-talk switch in the handset may respond and transmit speech currents out of the set circuit through the line terminals III, 20, and receive speech currents incoming over the telephone line terminals I9, 20. In the circuit arrangement shown in the figure, it is not necessary to crank the hand generator Ill! in receiving speech currents but only to transmit speech currents.

The word rectifying as used herein denotes the converting of the alternating current to direct current. The word fi1tering" as used herein denotes the smoothing out of the direct current wave, and the devices used to perform this function are called filters.

Although the preferred form of the invention as shown is a portable telephone set making use of a part of the switching device to disconnect the battery from the transmitter circuit, another form of the invention is a magneto telephone set without a battery, and which has only the hand generator output for supplying transmitter current. This form of the invention is useful for installation where the telephone set is relatively inaccessible for maintenance and where it may remain unused for long periods of time but where full efiiciency of transmission is imperative when it is used, as for example at an outlying coast artillery observation post.

What is claimed is:

1. A telephone set circuit comprising line terminals, a transmitting circuit connected across said terminals for generating and transmitting voice frequency current out of said set circuit, an alternating current hand'generator for signaling out of said set circuit and normally connected across said terminals, means for rectifying and filtering alternating current, and a hand operated switch for disconnecting said hand generator from said line terminals and connecting it to said rectifying and filtering means-and for connecting said rectifying, and filtering means into said transmitting circuit to constitute the sole source of transmitter current thereto.

2. A telephone set circuit comprising line terminals, a transmitting circuit connected across said terminals for generating and transmitting voice frequency current out of said set circuit, an alternating current hand generator for signaling out of said set circuit and normally connected across said terminals, means for converting alternating current to direct current and connected to a filter for smoothing the wave shape of said direct current, said filter being connected into said transmitting circuit, and a hand operable key for disconnecting said hand generator from said line terminals and connecting it to said rectifier whereby said generator constitutes the sole source of current in said transmitting circuit.

3.'A telephone set circuit comprising line terminals, a transmitting circuit connected across said terminals for generating and transmitting voice frequency current out of said set circuit, an alternating current hand generator for signaling out of said set circuit and normally connected across said terminals, a rectifier for converting alternating current to direct current and having input and output terminals, a filter network for smoothing the wave shape of direct current and having input and output terminals, said output terminals of said rectifier being connected to said input terminals of said filter network, said output terminals of said filter being connected into said transmitting circuit, and a hand operable switching key for disconnecting said hand generator from said line terminals and connecting it to said input terminals of said rectifier whereby said generator constitutes the sole source of current in said transmitting circuit.

CHARLES S. RHOADS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,396,760 Johnson Nov. 15, 1921 1,843,250 Spencer Feb. 2, 1932 2,050,292 Eaton Aug. 11, 1936 2,117,018 Conrad May 10, 1938 2,236,105 McLarn Mar. 25, 1941 2,305,378 Cypsen Dec. 15, 1942 2,346,548 Atkins Apr. 11, 1944 OTHER REFERENCES Miller: Telephone Theory and Practice, 1st edition, 1933 (page 364).

TM 11-1344 War Department Technical Manual, Dec. 15, 1944 (pages 9, and 27). 

